Electrochemical cell packaging material for housing an electrochemical cell body

ABSTRACT

Provided is a packaging material for electrochemical cells which has an identification mark that can be recognized from the outside and that is difficult to forge. The packaging material comprises a multilayer film which has a structure formed by laminating a base layer (11), an adhesive layer (13), a metal foil layer (12), an acid-modified polyolefin layer (14), and a heat-sealable layer (15) in this order, wherein the base layer (11) comprises both a oriented polyester film (11b) and a oriented nylon film (11e) with a printed layer (11c) provided on the surface of the oriented polyester film (11b) that faces the oriented nylon film (11e).

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. application Ser. No.15/061,652 filed Mar. 4, 2016, which is a divisional application of U.S.application Ser. No. 13/388,683 filed Feb. 3, 2012, now U.S. Pat. No.9,312,520B2, which is a U.S. National Stage Application filed under 35U.S.C. 371 of International Application No. PCT/JP2010/063260 filed Aug.5, 2010, designating the United States, and claims priority fromJapanese Patent Applications 2010-170323 and 2009-184850, filed on Jul.29, 2010 and Aug. 7, 2009, respectively, the complete disclosures ofwhich are incorporated herein for all purposes.

TECHNICAL FIELD

The present invention relates to an electrochemical cell packagingmaterial which has an identification mark that can be recognized fromthe outside and that is difficult to forge.

BACKGROUND ART

An electrochemical cell packaging material composed of a multilayer filmhas recently been used as an exterior body for electrochemical cellssuch as lithium ion batteries, lithium polymer batteries, and fuelcells, or liquid capacitors, solid capacitors, and double-layercapacitors which include liquid, solid ceramic, organic, or otherdielectrics, as described in Patent Citation 1, for example.

FIG. 4 is a sectional view showing the layer configuration of theconventional electrochemical cell packaging material, and as shown inFIG. 4, the conventional electrochemical cell packaging material 110 iscomposed of at least a base layer 111, a metal foil layer 112, and aheat-sealable layer 115, wherein the base layer 111 and the metal foillayer 112 are bonded via an adhesive layer 113, and the heat-sealablelayer 115 and the metal foil layer 112 are bonded via an acid-modifiedpolyolefin layer 114.

FIG. 5A is an exploded perspective view showing a lithium ion batterythat uses a conventional embossed-type exterior body, and FIG. 5B is aperspective view showing a lithium ion battery that uses theconventional embossed-type exterior body. As shown in FIGS. 5A and 5B, alithium ion battery 121 is fabricated by placing a lithium ion batterybody 122 in a tray 120 a having a concave part formed by cold pressingthe electrochemical cell packaging material 110 shown in FIG. 3 andblocking the open part of the tray 120 a with a sheet 120 b in a coldpress forming step, and overlaying the tray 120 a with the heat-sealablelayer 115 of the sheet 120 b and heat-sealing the edge thereof in asealing step.

In a lithium ion battery 121 fabricated in this manner, in the finalbattery manufacturing step, a label indicating product information andthe like is affixed to the surface of an exterior body 120, or productinformation and the like is printed by an inkjet directly on the surfaceof the exterior body 120 instead of using a label.

However, in a case in which a counterfeit lithium ion battery orelectrochemical cell packaging material from a manufacturer other thanthe authorized manufacturer bears the same identification mark as thatof an authorized manufacturer, it is difficult to distinguish between agenuine product and a counterfeit product.

LIST OF CITATIONS Patent Literature

Patent Citation 1: Japanese Laid-open Patent Publication No. 2007-273398

SUMMARY OF INVENTION Technical Problem

In order to overcome this problem, methods have been proposed for usinga hologram label in the identification mark to distinguish between agenuine product and a counterfeit product. However, hologram labels canraise the cost of the manufactured product, and there is also a riskthat a hologram label may be forged.

In view of the foregoing problems, an object of the present invention isto provide an electrochemical cell packaging material which has anidentification mark that can be recognized from the outside and that isdifficult to forge.

Solution to Problem

The present invention for achieving the abovementioned objects is anelectrochemical cell packaging material for housing an electrochemicalcell body, the electrochemical cell body including a positive electrodecomprising a positive-electrode active material and a positive-electrodecollector, a negative electrode comprising a negative-electrode activematerial and a negative-electrode collector, and an electrolyte filledbetween the positive electrode and the negative electrode; and sealingthe electrochemical cell body by heat-sealing of a peripheral edge partof the electrochemical cell packaging material; the electrochemical cellpackaging material characterized in that the electrochemical cellpackaging material is a multilayer film having a structure formed bylaminating at least a base layer, an adhesive layer, a metal foil layer,and a heat-sealable layer in this order; and any of the base layer, theadhesive layer, and the metal foil layer includes an identificationmark.

According to this configuration, since the identification mark isincluded in any of the base layer, the adhesive layer, and the metalfoil layer which constitute the electrochemical cell packaging material,the electrochemical cell packaging material as such serves as anidentifier, and authenticity can easily be determined even in a case inwhich printing is applied or a label is affixed as a forgedidentification mark on the electrochemical cell packaging material. Anyof the base layer, the adhesive layer, and the metal foil layer of theelectrochemical cell packaging material includes the identificationmark, and there is no need to provide an additional layer for theidentification mark. There is therefore no reduction in adhesivestrength between the base layer and the metal foil layer, and apredetermined adhesive strength can be maintained. Consequently, in acase in which the electrochemical cell packaging material is molded bypress molding or the like, the base layer and the metal foil layer canbe prevented from peeling apart to form bubbles or wrinkles due to heatapplied in a sealing step after molding.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that the base layerhas a oriented polyester film and a oriented nylon film; and theidentification mark is included between the oriented polyester film andthe oriented nylon film.

According to this configuration, the identification mark is protected bythe oriented polyester film, and the printed layer cannot be forged orworked from the outside of the electrochemical cell packaging material.By forming the identification mark between the oriented polyester filmand the oriented nylon film, there is no reduction in adhesive strengthbetween the oriented nylon film layer and the metal foil layer. Byforming the oriented polyester film as the outermost layer, in the casethat electrolytic solution or a solvent adheres to the surface of theelectrochemical cell packaging material, the oriented polyester filmprotects the oriented nylon film, and whitening or damage to theelectrochemical cell packaging material can be prevented.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that theidentification mark comprises a printed layer provided on a surface ofthe oriented polyester film that faces the oriented nylon film.

According to this configuration, the identification mark can easily beformed between the oriented polyester film and the oriented nylon filmby printing the identification mark on the surface of the orientedpolyester film and bonding together the oriented polyester film and theoriented nylon film. Printing also enables a complex design to be formedon the surface of the oriented polyester film, and an identificationmark can be formed that is difficult to forge.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that theidentification mark comprises a colored bonded layer interposed betweenthe oriented polyester film and the oriented nylon film.

According to this configuration, a colored layer can be formed betweenthe oriented polyester film and the oriented nylon film, and theelectrochemical cell packaging material can be identified by theimparted color. The authenticity of a product can therefore be easilydetermined by a color difference that can be recognized from the outsideof the electrochemical cell packaging material, even in a case in whichprinting is applied or a label is affixed as a forged identificationmark on the electrochemical cell packaging material.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that theidentification mark comprises the adhesive layer, the adhesive layerbeing colored.

According to this configuration, the electrochemical cell packagingmaterial can be identified by the color of the colored adhesive layer.The authenticity of a product can therefore be easily determined by acolor difference that can be recognized from the outside of theelectrochemical cell packaging material, even in a case in whichprinting is applied or a label is affixed as a forged identificationmark on the electrochemical cell packaging material. Since color isimparted to the adhesive layer as such for bonding the base layer andthe metal foil layer, there is no reduction in adhesive strength betweenthe base layer and the metal foil layer, and a predetermined adhesivestrength can be maintained.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that the base layercomprises a oriented nylon film; and the identification mark comprisesthe oriented nylon film, the oriented nylon film being colored.

According to this configuration, the electrochemical cell packagingmaterial can be identified by the color of the colored oriented nylonfilm. Since the base layer as such is colored, there is no reduction inadhesive strength between the base layer and the metal foil layer, and apredetermined adhesive strength can be maintained.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that theidentification mark comprises a unevenness applied to a metal foilsurface that constitutes the metal foil layer.

According to this configuration, the electrochemical cell packagingmaterial can be identified by the unevenness applied to the metal foilsurface. The authenticity of a product can therefore be easilydetermined by a unevenness that can be recognized from the outside ofthe electrochemical cell packaging material. Since a metal foil layerprovided with a unevenness is used, and the metal foil layer to whichthe unevenness is applied is laminated with the base layer via theadhesive layer, there is no reduction in adhesive strength between thebase layer and the metal foil layer, and a predetermined adhesivestrength can be maintained.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that theidentification mark is formed by including a pearl pigment in aconstituent resin.

According to this configuration, the electrochemical cell packagingmaterial is colored by a pearl pigment, and the electrochemical cellpackaging material can be identified by this color.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that theidentification mark is formed by including a fluorescent pigment in aconstituent resin.

According to this configuration, the electrochemical cell packagingmaterial is colored by the color development of the fluorescent pigment,and the electrochemical cell packaging material can be identified bythis color.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that a matte varnishlayer is formed on the base layer.

According to this configuration, a matting effect can be produced on thesurface of the base layer by forming a matte varnish layer on the baselayer. A design can thereby be formed by the base layer as a whole,together with the identification mark formed on the inside with respectto the base layer. The smoothness of the base layer surface is alsoincreased by the matte varnish layer, and molding defects in an embossedmolding step can be reduced. The smoothness can be adjusted at this timeby adjusting the amount of lubricant added to the matte varnish, and thematting effect can be adjusted by adjusting the particle diameter andadded amount of the matte material.

The electrochemical cell packaging material of the present inventionconfigured as described above is characterized in that a matte treatmentis applied on the base layer to impart a predetermined surface roughnessto a surface thereof.

According to this configuration, a matting effect can be produced on thesurface of the base layer by applying a matte treatment on the baselayer to impart a predetermined surface roughness thereto. A design canthereby be formed by the base layer as a whole, together with theidentification mark formed on the inside with respect to the base layer.With a matte film to which a matte treatment is applied by working thesurface thereof, the matting effect is not readily reduced by pressureor abrasion of the surface of the base layer during press molding. Thematting effect is also not readily reduced even in the case of adhesionof the electrochemical cell solvent.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing the layer configuration of theelectrochemical cell packaging material according to a first embodiment;

FIG. 2 is a sectional view showing the layer configuration of theelectrochemical cell packaging material according to a modification ofthe first embodiment;

FIG. 3 is a sectional view showing the layer configuration of theelectrochemical cell packaging material according to a secondembodiment;

FIG. 4 is a sectional view showing the layer configuration of theconventional electrochemical cell packaging material;

FIG. 5A is an exploded perspective view showing a lithium ion batterythat uses a conventional embossed-type exterior body; and

FIG. 5B is a perspective view showing a lithium ion battery that usesthe conventional embossed-type exterior body.

DESCRIPTION OF EMBODIMENTS First Embodiment

The electrochemical cell packaging material 10 according to a firstembodiment of the present invention will be described in detail withreference to the drawings. Portions that are the same as in theconventional examples shown in FIGS. 4 and 5 are not described. FIG. 1is a sectional view showing the layer configuration of theelectrochemical cell packaging material according to the firstembodiment of the present invention, and as shown in FIG. 1, theelectrochemical cell packaging material 10 of the present invention isconfigured such that a metal foil layer 12 is provided between a baselayer 11 as the outermost layer and a heat-sealable layer 15 as theinnermost layer, and the heat-sealable layer 15 and the metal foil layer12 are bonded via an acid-modified polyolefin layer 14. The base layer11 and the metal foil layer 12 are bonded via an adhesive layer 13. Atthis time, a chemical conversion layer 12 a is provided on a surface ofthe metal foil layer 12 that faces the acid-modified polyolefin layer14. The base layer 11 is composed of a matte varnish layer 11 a, aoriented polyester film 11 b, a printed layer 11 c, a bonded layer 11 d,and a oriented nylon film 11 e. The technical scope of the presentinvention includes cases in which the electrochemical cell packagingmaterial 10 of the present invention includes the abovementioned layers,as well as cases in which different layers are interposed between thelayers described above.

The printed layer 11 c and the matte varnish layer 11 a are formed byprinting and applying an ink material or matte varnish material to bothsides of the oriented polyester film 11 b. Through this configuration,the printed layer 11 c has the appearance of being decorated with amatte finish by the matte varnish layer 11 a when the electrochemicalcell packaging material 10 is viewed from the base layer 11 side. Thesmoothness of the surface of the base layer 11 is also increased by thematte varnish layer 11 a, and molding defects in an embossed moldingstep can be reduced. The smoothness of the surface of the base layer 11can be adjusted by adjusting the amount of lubricant added to the mattevarnish material, and the matte look (matting effect) of the mattevarnish layer 11 a can be adjusted by adjusting the particle diameterand added amount of the matte material that is included in the mattevarnish material.

Since the printed layer 11 c is formed on the surface of the orientedpolyester film 11 b that faces the oriented nylon film 11 e, the printedlayer 11 c is protected from the outside by the oriented polyester film11 b, and the printed layer 11 c cannot be forged or altered from theoutside of the electrochemical cell packaging material 10. The printedlayer 11 c is also not abraded when the surface of the electrochemicalcell packaging material 10 is abraded. Since the printed layer 11 c isformed between the oriented polyester film 11 b and the oriented nylonfilm 11 e, there is no reduction in adhesive strength between theoriented nylon film 11 e and the metal foil layer 12. The base layer 11and the metal foil layer 12 can therefore be prevented from peelingapart to form bubbles or wrinkles during press molding of theelectrochemical cell packaging material 10. By forming the orientedpolyester film 11 b as the outermost layer, in the case thatelectrolytic solution or a solvent adheres to the surface of theelectrochemical cell packaging material 10, the oriented polyester film11 b protects the oriented nylon film 11 e, and whitening or damage tothe electrochemical cell packaging material 10 can be prevented.

In plan view of the oriented polyester film 11 b, when the printed layer11 c is broadly formed, the entire electrochemical cell packagingmaterial 10 is colored, and when the printed layer 11 c is formed inlocalized fashion, an identification mark or design that is difficult toforge can be imparted to the printed layer 11 c The printed layer 11 ccan be formed using an ink material by gravure printing, silkscreenprinting, offset printing, or another publicly known printing method.

By using a oriented polyester film whose film surface is provided inadvance with a predetermined surface roughness as the oriented polyesterfilm 11 b, the surface of the base layer 11 can be decorated with amatte finish without forming a matte varnish layer 11 a. At this time,the matte look (matting effect) is less prone to be reduced by pressureor abrasion during press molding than that of the matte varnish layer 11a. The matte look (matting effect) is also not prone to be reduced byadhesion of the electrochemical cell solvent.

The layers constituting the electrochemical cell packaging material 10of the present invention shown in FIG. 1 will next be specificallydescribed.

A matte varnish in which an appropriate amount of silica-based,kaolin-based, or another inorganic material-based matting agent is addedto an alkyd-based synthetic resin or a cellulose-based, polyamide-based,vinyl acetate-based, modified polyolefin-based, rubber-based,acrylic-based, urethane-based, or other olefin-based resin, for example,may be used as the matte varnish layer 11 a. Alternatively, a mattevarnish may be used in which an appropriate amount of a wax and asilica-based, kaolin-based, or other inorganic material-based mattingagent is added to an alkyd-based synthetic resin or the aforementionedolefin-based resin. The method for forming the matte varnish layer isnot particularly limited, and an offset printing scheme, a gravureprinting scheme, a flexo printing scheme, a silkscreen printing scheme,a roll coating scheme, a reverse coating scheme, or the like, forexample, may be used as appropriate.

A polyester resin having ductility to withstand press molding may beused as the oriented polyester film 11 b, and specific polyester resinsinclude polyethylene terephthalate, polybutylene terephthalate,polyethylene naphthalate, polybutylene naphthalate, copolyester,polycarbonate, and the like.

The ink material used in the printed layer 11 c may be composed of abinder, a pigment, dye, or other colorant, and various additives addedthereto as appropriate, the same as a common ink. A chromatic colorpigment or an inorganic-based color pigment may be used as the colorant,and examples of chromatic color pigments include azo-based pigments,phthalocyanine-based pigments, condensed polycyclic pigments, and thelike. Watchung red, carmine 6C, and other soluble pigments, and monoazoyellow, disazo yellow, pyrazolone orange, red, permanent red, and otherinsoluble azo pigments can be cited as azo-based pigments. Copperphthalocyanine pigment can be cited as a phthalocyanine-based pigment.Non-metallic phthalocyanine pigments include blue and green-basedpigments, and dioxazine violet, quinacridone violet, and the like can becited as condensed polycyclic pigments. Titanium oxide, carbon black,and the like, for example, can be used as inorganic-based colorpigments.

An adhesive or a polyolefin resin can be used as the bonded layer 11 d,and specific examples of adhesives may include polyvinyl acetate-basedadhesives, ethyl and butyl acrylates, 2-ethylhexyl esters, and otherhomopolymers, or polyacrylic acid ester-based adhesives composed ofcopolymers or the like of the above compounds with methyl methacrylate,acrylonitrile, styrene, or the like; cyanoacrylate-based adhesives;ethylene copolymer-based adhesives composed of ethylene and vinylacetate, ethyl acrylate, acrylic acid, methacrylic acid, and othermonomers; cellulose-based adhesives; polyester-based adhesives;polyamide-based adhesives; polyimide-based adhesives; amino resin-basedadhesives composed of urea resin, melamine resin, or the like; phenolresin-based adhesives; epoxy-based adhesives; polyurethane-basedadhesives; reactive (meth)acrylic-based adhesives; rubber-basedadhesives composed of chloroprene rubber, nitrile rubber,styrene-butadiene rubber, and the like; silicone-based adhesives;inorganic-based adhesives composed of alkali metal silicates,low-melting glass, and the like; and other adhesives. The orientedpolyester film 11 b and the oriented nylon film 11 e can be bondedtogether by extruding a molten polyolefin resin therebetween, andspecific examples of polyolefin resins include polyethylene,polypropylene, and other heat-bondable resins.

The oriented nylon film 11 e may be a polyamide resin, specifically,nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10,poly meta-xylylene adipamide (MXD6), or the like.

The adhesive layer 13 is a layer in which the oriented nylon film 11 eand the metal foil layer 12 are bonded by a dry lamination method, andthe same adhesive as that of the bonded layer 11 d described above maybe used.

The metal foil layer 12 will next be described. The metal foil layer 12is a layer for preventing water vapor from penetrating into a lithiumion battery from the outside, and the metal foil layer may be a film orthe like on which aluminum, nickel, or other metal or an inorganiccompound, e.g., silicon oxide, alumina, or the like, is vapor-depositedto a thickness of 15 μm or greater in order to stabilize pinholing andprocessability (pouch formation, cold press moldability) of the metalfoil layer unit and impart anti-pinholing properties. However, the metalfoil that constitutes the metal foil layer 12 is preferably aluminumhaving a thickness of 20 to 100 μm.

In a case in which the occurrence of pinholing is reduced, and theexterior body of the lithium ion battery is the embossed type, thealuminum used as the metal foil layer 12 preferably has an iron contentof 0.3 to 9.0 wt %, preferably 0.7 to 2.0 wt %, in order to eliminatecracking and other defects in cold press molding.

The aluminum is thereby endowed with good ductility relative to aluminumthat contains no iron, pinholing due to folding is minimized in theexterior body, and side walls can easily be formed during cold pressmolding of the packaging material. In the case that the iron content isless than 0.3 wt %, pinholing is not prevented, and improved cold pressmoldability and other effects are not obtained, and in the case that theiron content of the aluminum is greater than 9.0 wt %, the flexibilityof the aluminum is inhibited, and the ability to form a bag with thepackaging material is reduced.

The flexibility and firmness/hardness of aluminum manufactured by coldrolling vary according to the annealing (so-called tempering process)conditions, but a partially or completely annealed aluminum that tendsto be flexible is preferred in the present invention over a hard-treatedproduct that is not annealed.

Specifically, the annealing conditions may be selected as appropriateaccording to processability (pouch formation, cold press molding). Forexample, in order to prevent wrinkling or pinholing during cold pressmolding, a flexible aluminum may be used that is annealed in accordancewith the degree of molding.

The strength of adhesion to the adhesive can also be enhanced byapplying a chemical conversion treatment to the front and back surfacesof the aluminum of the metal foil layer 12 to form the chemicalconversion layer 12 a.

The chemical conversion layer 12 a will next be described. As shown inFIG. 1, the chemical conversion layer 12 a is formed on at least thesurface of the metal foil layer 12 that faces the heat-sealable layer15. The chemical conversion layer 12 a is capable of stably bonding theacid-modified polyolefin layer 14 and the metal foil layer 12 andpreventing delamination of the metal foil layer 12 and the heat-sealablelayer 15. The chemical conversion layer 12 a also serves to preventcorrosion of the metal foil layer 12.

Specifically, by forming an antioxidant coating of a phosphate,chromate, fluoride, triazine thiol compound, or the like, it is possibleto prevent delamination between the metal foil layer 12 and theheat-sealable layer 15 during embossed molding, to prevent dissolutionand corrosion of the aluminum surface, particularly dissolution andcorrosion of the aluminum oxide that is present on the surface of thealuminum, due to hydrogen fluoride that occurs when the electrolyte ofthe lithium ion battery reacts with moisture, and to enhance theadhesion of the aluminum surface.

The chemical conversion layer 12 a is formed on the surface of the metalfoil layer 12 by a chromic acid chromate treatment, a phosphoric acidchromate treatment, an application-type chromate treatment, or otherchromium-based chemical conversion treatment, or a zirconium, titanium,zinc phosphate, or other non-chromium-based (application-type) chemicalconversion treatment or the like, but an application-type chemicalconversion treatment, particularly a treatment with a treatment fluidcontaining an aminated phenol polymer, a trivalent chromium compound,and a phosphorus compound, is most preferred in terms of strong adhesionto fluorine-based resins, and low processing cost due to the ability toperform continuous processing and no need for a rinsing step.

The heat-sealable layer 15 will next be described. The innermostheat-sealable layer 15 is held and heat-bonded in a state in which metalterminals of the lithium ion battery body 122 protrude to the outside.At this time, the type of propylene that constitutes the heat-sealablelayer 15 varies according to whether an adhesive film for sealing themetal terminals, which is adhesive to metal, is present between theheat-sealable layer 15 and the metal terminals. In the case that theadhesive film for sealing the metal terminals is present, a filmcomposed of a single propylene-type resin or a mixture thereof may beused, but in the case that there is no adhesive film for sealing themetal terminals, a film must be used that is composed of anacid-modified olefin resin that is graft modified by an unsaturatedcarboxylic acid.

Polypropylene is suitable for use as the heat-sealable layer 15, but afilm may also be used that is composed of one or more layers of linearlow-density polyethylene or mid-density polyethylene, or one or morelayers of a blended resin of linear low-density polyethylene andmid-density polyethylene. Polypropylene may be classified into randompropylene, homopropylene, block propylene, and other types.

Low-crystallinity ethylene-butene copolymer, low-crystallinitypropylene-butene copolymer, terpolymers composed of three-componentcopolymers of ethylene, butene, and propylene, silica, zeolite, acrylicresin beads, and other anti-blocking agents (AB agents), fatty acidamide-type slip agents, and the like may be added to the abovementionedtypes of polypropylenes, i.e., random polypropylene, homopolypropylene,and block polypropylene.

The heat-sealable layer 15 according to the present invention may alsobe endowed with a multilayer structure by combining the abovementionedtypes of polypropylenes at an appropriate time.

The acid-modified polyolefin layer 14 will next be described. Theacid-modified polyolefin layer 14 is a layer provided for bonding themetal foil layer 12 and the heat-sealable layer 15, and although thematerial thereof must be appropriately selected for use according to thetype of resin used in the heat-sealable layer 15, an acid-modifiedpolyolefin resin may be used, and the acid-modified polyolefin layer 14is a polyolefin resin that is graft modified by an unsaturatedcarboxylic acid, a copolymer of ethylene or propylene with acrylic acidor methacrylic acid, or a metal cross-linked polyolefin resin or thelike, and 5% or more of a butene component, ethylene-propylene-butenecopolymer, non-crystalline ethylene-propylene copolymer,propylene-α-olefin copolymer, or the like may also be added thereto.

Using an acid-modified polypropylene as the acid-modified polyolefinlayer 14 makes it possible to provide an electrochemical cell packagingmaterial 10 having even better adhesive strength and resistance tocontents.

In the case that an acid-modified polypropylene is used, (1) a homo-typehaving a Vicat softening point of 115° C. or higher and a melting pointof 150° C. or higher, (2) a copolymer (random copolymer type) ofethylene and propylene having a Vicat softening point of 105° C. orhigher and a melting point of 130° C. or higher, or (3) a simple orblended substance which is acid-modified using an unsaturated carboxylicacid, having a melting point of 110° C. or higher may be used.

A modification of the first embodiment will next be described. FIG. 2 isa sectional view showing the layer configuration of the electrochemicalcell packaging material according to a modification of the firstembodiment, and portions thereof that are the same as the firstembodiment are referred to by the same reference symbols. As shown inFIG. 2, by coloring the bonded layer 11 d with titanium oxide or anothercolor pigment instead of the printed layer 11 c, an identification markcan be formed in the bonded layer 11 d. According to this configuration,the bonded layer 11 d is colored white by the titanium oxide, and theelectrochemical cell packaging material 10 is identified by the whitecolor viewed from the side of the transparent oriented polyester film 11b. The authenticity of a product can therefore be easily determined by acolor difference that can be recognized from the outside of theelectrochemical cell packaging material 10, even in a case in whichprinting is applied or a label is affixed as a forged identificationmark on the surface of the base layer 11 of the electrochemical cellpackaging material 10.

The bonded layer 11 d is preferably composed of an adhesive to whichtitanium oxide or another color pigment is added to give a solidscontent of 5 wt % or greater and 30 wt % or less, preferably 10 wt % orgreater and 25 wt % or less. The imparted color is thin and difficult toidentify when the added quantity of the color pigment is less than 5 wt%. The adhesive strength decreases when the added quantity of the colorpigment exceeds 30 wt %. Shading of the imparted color can be expressedby adjusting the added quantity of the color pigment, and theelectrochemical cell packaging material 10 can also be identified by theshading of the color. The adhesive used may be an adhesive cited aboveas a specific example of the bonded layer 11 d. The technical scope ofthe present invention also encompasses an embodiment in whichpolyethylene or another polyolefin resin blended with a color pigment isextruded in a molten state and laminated with the oriented polyesterfilm 11 b and the oriented nylon film 11 e.

A chromatic color pigment or an inorganic-based color pigment may beused as the color pigment, and examples of chromatic color pigmentsinclude azo-based pigments, phthalocyanine-based pigments, condensedpolycyclic pigments, and the like. Watchung red, carmine 6C, and othersoluble pigments, and monoazo yellow, disazo yellow, pyrazolone orange,red, permanent red, and other insoluble azo pigments can be cited asazo-based pigments. Copper phthalocyanine pigment can be cited as aphthalocyanine-based pigment. Non-metallic phthalocyanine pigmentsinclude blue and green-based pigments, and dioxazine violet,quinacridone violet, and the like can be cited as condensed polycyclicpigments. Titanium oxide, carbon black, and the like, for example, canbe used as inorganic-based color pigments.

The bonded layer 11 d can be colored by titanium oxide or another colorpigment, as well as by a pearl pigment or fluorescent pigment.Traditionally, pearl powder or powder made from the inside portion of ashell was used as pearl pigment, but fine flakes (chips) coated on theoutside with a metal oxide or metal oxide mixture are now used. The fineflakes may be mica, talc, kaolin, or bismuth oxychloride, or glassflakes, SiO₂ flakes, synthetic ceramic flakes, or the like, and examplesof metal oxides for coating the outside of the fine flakes include TiO₂,Fe₂O₃, SnO₂, Cr₂O₃, and ZnO. Among combinations of these substances,mica, glass flakes, or SiO₂ flakes coated with TiO₂ and/or Fe₂O₃ arepreferred. Fluorescent pigments are phosphors, i.e., substances whichare generally luminescent, and include both inorganic fluorescentpigments and organic fluorescent pigments. Pigments primarily composedof crystals of oxides, sulfides, silicates, phosphates, tungstates, andthe like of Ca, Ba, Mg, Zn, Cd and the like which are obtained bysintering after adding Mn, Zn, Ag, Cu, Sb, Pb or another metal elementor a lanthanoid or rare earth element as an activating agent can be usedas inorganic fluorescent pigments. Examples of preferred phosphorsinclude ZnO:Zn, Br₃(PO₄)₃Cl:Eu, Zn₂GeO₄:Mn, Y₂O₃:Eu, Y(P,V)O₄:Eu,Y₂O₂Si:Eu, Zn₂GeO₄:Mn, and the like, and diaminostilbenedisulfonic acidderivatives, imidazole derivatives, coumarin derivatives, triazoles,carbazoles, pyridines, naphthalic acid, imidazolones, and otherpigments, anthracines and other compounds which have a benzene ring, andthe like can be used as organic fluorescent pigments.

Second Embodiment

The electrochemical cell packaging material according to a secondembodiment of the present invention is described below with reference tothe drawings. The same reference symbols are used to refer to portionsof the second embodiment that are the same as the first embodiment, andno description thereof is given. FIG. 3 is a sectional view showing thelayer configuration of the electrochemical cell packaging material ofthe present invention, and as shown in FIG. 3, the base layer 11 of theelectrochemical cell packaging material 10 of the second embodiment iscomposed of the oriented nylon film 11 e, and the oriented nylon film 11e and the metal foil layer 12 are bonded via the adhesive layer 13.

Here, the adhesive layer 13 is composed of an adhesive which containstitanium oxide or another color pigment, and the adhesive layer 13 iscolored white. The electrochemical cell packaging material 10 is therebyidentified by the white color viewed from the side of the transparentoriented nylon film 11 e. Since the adhesive layer 13 as such forbonding the oriented nylon film 11 e and the metal foil layer 12includes a color pigment, there is substantially no reduction inadhesive strength between the oriented nylon film 11 e and the metalfoil layer 12. Consequently, in a case in which the electrochemical cellpackaging material 10 is molded by press molding or the like, theoriented nylon film 11 e and the metal foil layer 12 can be preventedfrom peeling apart to form bubbles or wrinkles due to heat applied in asealing step after molding.

The adhesive layer 13 is preferably composed of an adhesive to whichtitanium oxide or another color pigment is added to give a solidscontent of 5 wt % or greater and 30 wt % or less, preferably 10 wt % orgreater and 25 wt % or less. The imparted color is thin and difficult toidentify when the added quantity of the color pigment is less than 5 wt%. When the added quantity of the color pigment exceeds 30 wt %, theadhesive strength between the oriented nylon film 11 e and the metalfoil layer 12 decreases, the heat applied in the sealing step aftermolding causes the oriented nylon film 11 e to shrink so as to return tothe original shape thereof, and the oriented nylon film 11 e and metalfoil layer 12 to peel apart and form bubbles or wrinkles. Shading of theimparted color can be expressed by adjusting the added quantity of thecolor pigment. The electrochemical cell packaging material 10 canthereby also be identified by the shading of the color.

The color pigment may be titanium oxide or another color pigment citedin the first embodiment, or the adhesive layer 13 may be colored using apearl pigment or fluorescent pigment cited in the first embodiment. Anadhesive cited for use in the bonded layer 11 d of the first embodimentmay also be used as the adhesive for forming the adhesive layer 13.

The same effects can be obtained in the adhesive layer 13 even when anadhesive that is not colored is used instead of an adhesive thatcontains titanium oxide or another color pigment, and the oriented nylonfilm 11 e is colored. In other words, the electrochemical cell packagingmaterial 10 can be identified by the color of the oriented nylon film 11e which is colored by inclusion of a color pigment, and by coloring thebase layer 11 as such, a predetermined adhesive strength can bemaintained without reducing the adhesive strength of the base layer 11and the metal foil layer 12. Using a oriented nylon film 11 e whosesurface is matte treated also increases the smoothness of the surface ofthe electrochemical cell packaging material 10, and molding defects in acold press molding step can be reduced. The same effects can be obtainedwhen the abovementioned matte varnish layer 11 a is formed on theoriented nylon film 11 e instead of applying a matte treatment to theoriented nylon film 11 e.

The same effects can also be obtained in the metal foil layer 12 throughuse of a metal foil subjected to a matte treatment having a fineunevenness on the surface thereof, or a metal foil having localizedunevenness, instead of using a colored adhesive layer 13 or orientednylon film 11 e. In other words, the electrochemical cell packagingmaterial 10 can be identified by the unevenness provided to the metalfoil surface that constitutes the metal foil layer 12, and theauthenticity of a product can be easily determined by a unevenness thatcan be recognized from the outside of the electrochemical cell packagingmaterial 10 even in a case in which printing is applied or a label isaffixed as a forged identification mark on the electrochemical cellpackaging material 10. Since a metal foil provided with a fineunevenness is used as the metal foil that constitutes the metal foillayer 12, there is no reduction in adhesive strength between the baselayer 11 and the metal foil layer 12.

The present invention is not limited to the embodiments described above,various modifications thereof are possible, and the technical scope ofthe present invention also encompasses embodiments obtained byappropriately combining the technical means disclosed in each of thedifferent embodiments. For example, an identification mark may be formedby a combination of any or all of the matte varnish layer 11 a, theprinted layer 11 c, the colored bonded layer 11 d, the colored orientednylon film 11 e, the colored adhesive layer 13, and the metal foil layer12 in which a unevenness is formed, or an identification mark may beformed from any one of the above constituent elements. Combining theseconstituent elements allows a complex design to be formed that is moredifficult to forge.

In the embodiments, the acid-modified polyolefin layer 14 is providedbetween the metal foil layer 12 and the heat-sealable layer 15, but thetechnical scope of the present invention also encompasses embodiments inwhich the acid-modified polyolefin layer 14 is not provided.Specifically, the technical scope of the present invention encompassesembodiments in which an adhesive layer other than an acid-modifiedpolyolefin resin is provided between the metal foil layer 12 and theheat-sealable layer 15, embodiments in which an acid-modified polyolefinresin is used in the heat-sealable layer 15, embodiments in which achemically converted metal foil layer 12 and heat-sealable layer 15 areheat-laminated, and other embodiments.

Example 1

The operations and effects of the present invention are specificallydescribed below using examples. Example 1 is an evaluation of themolding suitability and laminate strength of the electrochemical cellpackaging material. In this experiment, electrochemical cell packagingmaterials fabricated using different amounts of color pigment added tothe adhesive layer are compared in order to confirm the moldingsuitability and laminate strength of the electrochemical cell packagingmaterial in the case that a color pigment is added to the adhesive layerthat constitutes the electrochemical cell packaging material.

[Fabrication of Packaging Material Samples]

A chemical conversion treatment was applied on both sides of aluminum(thickness: 40 μm), a oriented nylon film (thickness: 25 μm) was affixedto one chemical-conversion-treated surface by a dry lamination methodvia a polyester-based adhesive so as to give a thickness ofapproximately 4 μm of the adhesive layer, an acid-modified polypropylene(thickness: 23 μm) was melt-extruded onto the otherchemical-conversion-treated surface and a sealant film composed of apolypropylene film (thickness: 23 μm) was laminated thereon, and aelectrochemical cell packaging material was obtained which was composedof a oriented nylon film, a polyester-based adhesive, aluminum treatedon both sides with a chemical conversion treatment, an acid-modifiedpolypropylene, and a polypropylene film in this order.

At this time, an aqueous solution composed of phenol resin, a chromiumfluoride compound, and phosphoric acid was used as the treatment fluidin each chemical conversion treatment, which was applied by rollcoating, and sintering was performed to give a coating temperature of180° C. or higher. The amount of chromium applied was 10 mg/m² (dryweight).

Adhesives in which titanium oxide as the color pigment was added to apolyester-based adhesive to give a solids content of 0 wt %, 5 wt %, 10wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt %, 40 wt %, and 50 wt % wereused, and the electrochemical cell packaging materials obtained weredesignated as Samples 1 through 9. Samples 2 through 9 were theelectrochemical cell packaging material of the present invention.

In a packaging material obtained by the method described above, insteadof adding a color pigment to the polyester-based adhesive, a printedlayer (thickness: 2 μm) of urethane-based ink to which titanium oxide asa color pigment was added to give a solids content of 15 wt % was formedon one side of the oriented nylon film (thickness: 25 μm), and anelectrochemical cell packaging material of a comparative example wasobtained, composed of a oriented nylon film, a printed layer, apolyester-based adhesive, aluminum treated on both sides with a chemicalconversion treatment, an acid-modified polypropylene, and apolypropylene film in this order.

[Evaluation of Moldability]

The electrochemical cell packaging materials of Samples 1 through 9 andthe comparative example fabricated by the method described above werecut into 120×80 mm strips, and using a straight mold (male mold cornerR: 2 mm, ridge line R: 1 mm) composed of a 55×32 mm rectangular positivemold and a negative mold having a 0.3 mm clearance with the positivemold, a strip was mounted on the negative mold so that the heat-sealablelayer was positioned facing the positive mold, the strip was pressed ata pressure (contact pressure) of 0.16 MPa, and the electrochemical cellpackaging materials of Samples 1 through 9 and the comparative examplewere cold press molded to a molding depth of 6 mm. The electrochemicalcell packaging materials of Samples 1 through 9 and the comparativeexample were thereby each made into a molded container (tray) having a55×32 mm rectangular concave part with a depth of 6 mm, and a flangepart at the four peripheral edges of the concave part.

A strip having substantially the same size as the outer circumference ofthe tray was then separately prepared, the concave part was coveredsubstantially even with the flange part, and two peripheral edges of theconcave part were heat sealed at a width of 7 mm. Heat sealing at thistime was performed using a hot plate coated on the top and bottom with afluorine-based resin coating, using a sealing temperature of 190° C., acontact pressure of 1 MPa, and a sealing time of 3.0 seconds. Theincidence of bubbles, wrinkles, or peeling apart at the intersections ofthe 7 mm-width heat seal was evaluated, as shown in Table 1. Table 1also shows an evaluation of the apparent color due to the color pigmentthat was recognizable from the side of the oriented nylon film of theelectrochemical cell packaging material.

[Evaluation by Measurement of Laminate Strength]

Each packaging material fabricated as described above was then cut intoa 15 mm-wide strip, tension was applied between the aluminum and thebase layer as the outermost layer of the laminated electrochemical cellpackaging material at a speed of 50 mm/minute by a tensile tester(AGS-50D (trade name), manufactured by Shimadzu Seisakusho) to measurethe laminate strength, and the measured value was designated as theelectrolyte-resistant laminate strength. The units thereof are N/15 mmof width. Table 1 shows the laminate strength measured for theelectrochemical cell packaging materials of Samples 1 through 9 and thecomparative example.

TABLE 1 Color pigment Laminate strength (solid content %) (N/15 mm)Moldability Color Sample 1 0 Break ∘ — Sample 2 5 Break ∘ Δ Sample 3 10Break ∘ ∘ Sample 4 15 Break ∘ ∘ Sample 5 20 Break ∘ ∘ Sample 6 25 Break∘ ∘ Sample 7 30 8.0 ∘ ∘ Sample 8 40 6.0 x ∘ Sample 9 50 4.0 x ∘Comparative — 4.0 x ∘ Example

As shown in Table 1, it was apparent by comparing Samples 1 through 9and the comparative example that good moldability was obtained inSamples 1 through 7. Specifically, wrinkling and interlayer peeling wereobserved (x) in cases in which the color pigment was added in the amountof 40% or more to the adhesive, such as in Samples 8 and 9, and in thecase that a printed layer composed of ink was provided, as in thecomparative example. On the other hand, no wrinkling or interlayerpeeling was observed in Samples 1 through 7 (◯).

When the color pigment was added in the amount of 5% in Sample 2, theadhesive was not adequately colored, and coloration was difficult toidentify from the outside (Δ), whereas in Samples 3 through 9, in whichthe color pigment was added in the amount of 10% or more, the adhesivewas colored, allowing identification from the outside (◯).

Samples 2 through 6 were devoid of bubbles, and the laminate strengththereof was unchanged from that of Sample 1. Sample 7 was devoid ofbubbles but had reduced laminate strength.

Based on the above results, it is apparent that an electrochemical cellpackaging material formed by adding 10% or more and 30% or less oftitanium oxide as a color pigment to a polyester-based adhesivefunctions as an identification mark that is difficult to forge and whosecolor is recognizable from the outside, and that heat applied in asealing step subsequent to molding does not cause interlayer peeling andconsequent formation of bubbles or wrinkles.

LIST OF REFERENCE SIGNS

-   -   10, 110 electrochemical cell packaging material    -   11, 111 base layer    -   11 a matte varnish layer    -   11 b oriented polyester film    -   11 c printed layer    -   11 d bonded layer    -   11 e oriented nylon film    -   12, 112 metal foil layer    -   12 a, 112 a chemical conversion layer    -   13, 113 adhesive layer    -   14, 114 acid-modified polyolefin layer    -   15, 115 heat-sealable layer    -   120 exterior body    -   120 a tray    -   120 b sheet    -   121 lithium ion battery    -   122 lithium ion battery body

The invention claimed is:
 1. An electrochemical cell packaging materialfor housing an electrochemical cell body, the electrochemical cell bodyincluding a positive electrode comprising a positive-electrode activematerial and a positive-electrode collector, a negative electrodecomprising a negative-electrode active material and a negative-electrodecollector, and an electrolyte; and sealing said electrochemical cellbody by heat-sealing of a peripheral edge part of the electrochemicalcell packaging material, said electrochemical cell packaging materialcharacterized in that the electrochemical cell packaging material is amultilayer film having a structure formed by laminating at least a baselayer, an adhesive layer, a metal foil layer, and a heat-sealable layerin this order from outside, the heat-sealable layer being arranged as aninnermost layer, and said adhesive layer comprises a pigment.
 2. Theelectrochemical cell packaging material according to claim 1, whereinsaid adhesive is one selected from the group consisting of a polyvinylacetate-based adhesive, a polyacrylic acid ester-based adhesive, acyanoacrylate-based adhesive, an ethylene copolymer-based adhesive, acellulose-based adhesive, a polyester-based adhesive, a polyamide-basedadhesive, a polyimide-based adhesive, an amino resin-based adhesive, aphenol resin-based adhesive, an epoxy-based adhesive, apolyurethane-based adhesive, a reactive acrylic-based adhesive, asilicone-based adhesive, an inorganic-based adhesive comprising analkali metal silicate, and an inorganic-based adhesive comprisinglow-melting glass.
 3. The electrochemical cell packaging materialaccording to claim 1, characterized in that said base layer has aoriented polyester film and a oriented nylon film; and a printed layeris provided on a surface of said oriented polyester film that faces saidoriented nylon film.
 4. An electrochemical cell packaging material forhousing an electrochemical cell body, the electrochemical cell bodyincluding a positive electrode comprising a positive-electrode activematerial and a positive-electrode collector, a negative electrodecomprising a negative-electrode active material and a negative-electrodecollector; and sealing said electrochemical cell body by heat-sealing ofa peripheral edge part of the electrochemical cell packaging material,said electrochemical cell packaging material characterized in that theelectrochemical cell packaging material is a multilayer film having astructure formed by laminating at least a base layer, an adhesive layer,a metal foil layer, and a heat-sealable layer in this order fromoutside, the heat-sealable layer being arranged as an innermost layer,said base layer has a oriented polyester film and a oriented nylon film;and a bonded layer containing a pigment is interposed between saidoriented polyester film and said oriented nylon film.
 5. Theelectrochemical cell packaging material according to claim 1,characterized in that said base layer comprises a colored oriented nylonfilm.
 6. The electrochemical cell packaging material according to claim1, characterized in that an unevenness is applied to a metal foilsurface that constitutes said metal foil layer.
 7. The electrochemicalcell packaging material according to claim 4, characterized in that saidadhesive layer is formed by including a pearl pigment in a constituentresin.
 8. The electrochemical cell packaging material according to claim4, characterized in that said adhesive layer is formed by including afluorescent pigment in a constituent resin.
 9. The electrochemical cellpackaging material according to claim 1, characterized in that a mattevarnish layer is formed on said base layer.
 10. The electrochemical cellpackaging material according to claim 1, characterized in that a mattetreatment is applied on said base layer to impart a predeterminedsurface roughness to a surface thereof.